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Stumped with fuel delivery problem.

The drivetrain is 2004 Mach 1, DOHC 32V, Mustang fuel tank, pump etc. Here is the dilemma: Turning the key to the on/acc position the fuel pump will come on, pressurize the system and stop, like it normally would. Turn the key to the crank position and the vehicle will start, but the fuel pump will NOT kick back on, therefore the engine only runs for a few seconds. Changed out the fuel pump, fuel pump control module, the crank trigger sensor. Double and triple checked wiring, matches up with the schematics from the Mustang, have plenty of ground wires that have also been triple checked. The computer was flashed by Ron Francis to ONLY remove the PATS and after cat O2 sensors. ANY help or information is appreciated. This has been going on for far too long. I prefer to keep this set up, but if I can't figure it out I'll be forced to get a complete new fuel system, which I don't want to do. Had it hooked up to a Ford dealer scan tool, no codes came up.

I chased fuel pump wiring problems and finally got the electrical correct but still wouldn't start. Discovered the fuel pick up hose had slipped off. Fixed that and it would start but then quickly died. I assumed it was still fuel pump related but found out I had my MAF sensor in backwards. Flipped it and runs like a champ

So what you're saying is; Fuel pump comes on at initial start sequence, turning the key to ON, you get a single pulse to the pump (normal). Then when you crank the engine over, there is NO fuel pump function (I believe that's normal). Then when the key is returned to ON to keep the engine running, there is no fuel pump function? How am I doing so far??

To the best of my knowledge, The fuel pump needs to "see" the engine [actually] running and that function is controlled by the crank trigger. Once the engine is spinning, the pickup at the crank trigger constantly re-triggers the fuel pump to cycle again and again.
If possible, check your wiring at the crank trigger to ensure that the trigger pulses are in fact happening - sounds like they are if the engine will run until the fuel pressure drops off to a point where the engine won't continue. That being said, you may be getting the trigger pulses for ignition but not the fuel pump, causing the pump to NOT run.

IF the inertia switch was bad, you wouldn't get the initial pump run cycle, it's in series to the power lead to the pump. It's either open or closed, not intermittent.

If your fuel pump runs and gets to design pressure, it's not the fuel pump.

Gentlemen, I have no idea how to do the "quotes" thing. So I'll answer in order:

John, It will come on just for an instant and when the engine fires it will not come back on.

Rick, the initial pressure is at 45-47 psi, after it starts it will slowly drop and the engine will die.

Doc, first paragraph, yes, yes, and yes. I'll double check the wiring at the crank trigger pickup. Hmmm how could I get a crank trigger pulse for ignition, but not the pump? I've eliminated the fuel pump as the issue, put in two different ones. We have wired the fuel pump to run constantly to eliminate it. The engine runs fine that way. I know the factory pump is not designed for that type of operation, it was just a trial of two-three minutes.

Erik, how would I actually test to see if the PATS is actually disabled ?

Thanks again, this forum is invaluable for things like this. Unfortunately I don't have the "normal" engine to help out that many people.

I have a PATS disabled car here I am working on. I believe its a 99 Computer and harness. When PATS is active, it kills the injector power too. Maybe this is specific to this year, but something to look into on yours. Sounds like you have injector power.
Mike

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